For example, in a conventional steering control device described in PTL 1, firstly, a current command value 1 is calculated from a steering torque after phase compensation (the sum of a steering torque and a signal proportional to the differential of the steering torque) with a graph of the characteristics of a motor current command value in the assist direction. Furthermore, a current command value 2 is calculated from a signal proportional to the differential of the steering torque. In this way, motor assist control is carried out on the basis of the sum of the current command value 1 and the current command value 2.
In the conventional steering control device described in PTL 1, self-induced vibration is prevented by calculating the current command value 1 from the steering torque after phase compensation. Furthermore, the effects of the motor inertia are suppressed by calculating the current command value 2 from a signal proportional to the differential of the steering torque.
Although not described in PTL 1, the current command value 2 calculated from the signal proportional to the differential of the steering torque also has an effect of suppressing the transmission, to the driver, of road surface vibrations produced when travelling over bad roads, etc.